Method and device for making slit walls

ABSTRACT

PROPOSED IS A METHOD OF MAKING SLIT WALLS, WHEREIN A SLIT WALL SECTION PRESENT IN THE SOIL AND FILLED WITH A THIXOTROPIC LIQUID IN A KNOWN MANNER IS EXCAVATED AND RESPECTIVELY DRIVEN AHEAD AT A FRONT END BY MEANS OF A BUCKET CHAIN EXCAVATOR. ON THIS OCCASION, THE BUCKET CHAIN EXCAVATOR IS SEALED OFF AGAINST THE IDE WALLS OF THE EXCAVATED SLIT AND AGAINST THE SOLE OF THE SLIT SO THAT LIQUIDFILLED SPACES SEPARATE FROM EACH OTHER ARE CREATED IN FRONT AND IN THE REAR OF THE BUCKET CHAIN EXCAVATOR RESPECTIVELY. FOR PRODUCING THE DRIVE-ON FORCE FOR THE BUCKET CHAIN EXCAVATOR, THE LIQUID LEVEL IN THE SPACE LOCATED IN FRONT OF THE BUCKET CHAIN EXCAVATOR IS LOWERED AS COMPARED TO THE LIQUID LEVEL IN THE SPACE LOCATED BEHIND THE BUCKET CHAIN EXCAVATOR SO THAT THE BUCKET CHAIN EXCAVATOR IS DRIVEN FORWARD BY THE ROSTATIC PRESSURE DIFFERENTIAL. THE SLIT MADE IN THIS MANNER IS SUBSEQUENTLY FILLED UP WITH CONCRETE.   D R A W I N G

Feb. 23, 1971 J MQRNER 3,564,855

METHOD AND DEVICE FOR MAKING SLIT WALLS Filed MarCh 20, 1969 3Sheets-Sheet l INVF N (OR JOHANN M ORNEH BY ATTORNEY Feb. 23, 1971 J.MORNER METHOD AND DEVICE FOR MAKING SLIT WALLS Filed March 20, 1969 3Sheets-Sheet 2 INVFN'TOH JOHANN MO'RNER K 7 MA V AT I'ORNLY Feb. 23,1971 MRNER 3,564,855 7 METHOD AND DEVICE you MAKING :3I..1"r WALL};

Filed March 20, 1969 3 SheetsSheet 3 v mm #4 ran JOHANN MUHNF H ATTORNEYUnited States Patent O1 fice 3,564,855 METHOD AND DEVICE FOR MAKING SLITWALLS Johann Miirner, 8207 Endorf, Kurf 7, Germany Filed Mar. 20, 1969,Ser. No. 808,757 Claims priority, application Germany, Apr. 8, 1968,

, P 17 59 188.7 Int. Cl. E02d 5/18 US. Cl. 61-35 14 Claims ABSTRACT OFTHE DISCLOSURE Proposed is a method of making slit walls, wherein a slitwall section present in the soil and filled with a thixotropic liquid ina known manner is excavated and respectively driven ahead at a front endby means of a bucket chain excavator. On this occasion, the bucket chainexcavator is sealed off against the side walls of the excavated slit andagainst the sole of the slit so that liquid filled spaces separate fromeach other are created in front and in the rear of the bucket chainexcavator respectively. For producing the drive-on force for the bucketchain excavator, the liquid level in the space located in front of thebucket chain excavator is lowered as compared to the liquid level in thespace located behind the bucket chain excavator so that the bucket chainexcavator is driven forward by the hydrostatic pressure differential.The slit made in this manner is subsequently filled up with concrete.

BACKGROUND OF THE INVENTION This invention relates to methods anddevices for making slit walls.

The slit wall construction practice has acquired a great technicalimportance in recent years especially for the municipal traificengineering, e.g., for constructing subways. Yet for makingconstructions in busy townships it is particularly important to maintainthe time of construction as short as possible in order to reduce anyinterruptions of the trailic.

A number of various methods have heretofore been developed for makingslit walls, and the slits for the slit walls are excavated mostly bymeans of rope grabs.

However, it turned out that the grab dredging technique just as thevarious other methods are very timeconsurning, which has unfavourableconsequences and in some cases particularly jeopardizes theprofitableness of the slit wall building technique.

Also, by the prior art methods it is mostly impossible to avoid cavitieswhich are formed in adjacent earth areas and lead to a needlessly highconsumption of concrete as well as to uneven wall surfaces; according tothe known methods, it is also necessary to employ separate endshuttings-off or end shutterings such as, e.g., steel tubes forconcreting the slit walls, which is a complicated and expensivepractice.

SUMMARY OF THE INVENTION The object of the invention is to provide amethod permitting a more rapid, rationalized and economical execution ofthe construction work for making slit walls.

This and other objects of the invention are achieved by a method ofmaking slit walls, wherein a slit section present in the ground isfilled with a fluid and excavated at a front end substantiallycontinuously by means of a bucket chain excavator, wherein the bucketchain excavator is sealed off against the side walls of the excavatedslit and against the sole of the slit so that at the side of the bucketchain excavator facing said front end of the slit and within the slitthere is formed a first fluid-filled 3,564,855 Patented Feb. 23, 1971space separate from the second fluid-filled space located behind thebucket chain excavator, and wherein the fluid level in said firstfluid-filled space is lowered as compared to the fluid level in saidsecond fluid-filled space so that the bucket chain excavator is drivenforward by the hydrostatic pressure differential, and finally, whereinthe formed slit is subsequently filled up with concrete.

For securing the earth, the slit is filled with a thixotropic fluid inany case. Hence the force required for the forward drive is obtained inthat the liquid level in the working space surrounded by the bucketchain excavator at the end face of the slit is maintained lower than inthe slit region lying therebehind. In this manner it is achieved that apractically uniformly distributed drive-on force acts on the bucketchain excavator, whereby providing the possibility of the effective useof a bucket chain excavator.

A further object of the invention is to provide a device for carryingout the method according to the invention. The device includes avertical U-shaped steel box, on which two endless and laterallytelescoping bucket chains are disposed so that, running from belowupwards, they break the soil loose at the front side of the slit and digit. The steel box is slightly narrower than the slit to be formed. Thespace between the steel box and the lateral earth is bridged over bysuitable seals so that the working space enclosed by the steel box issealed off from the remaining slit.

According to a preferred embodiment of the invention, the back side ofthe steel box is formed in a fashion favourable for the concretingjoints so that during the concreting of the slit walls the steel box canbe simultaneously utilized as a joint shuttering too.

The guidance of the bucket chain excavator in the forward drivedirection, especially when curved slit walls are to be produced, isenabled by a guide arm arranged on the device above the level of theterrain.

BRIEF DESCRIPTION OF THE DRAWINGS- The invention is elucidated ingreater detail hereinafter in the light of exemplary embodiments withreference to the drawings, in which:

FIG. 1a shows a horizontal section through a bucket chain excavatoraccording to the invention,

FIG. 1b shows a horizontal section through a bucket chain excavator withanother structure of the back side of the steel box, and

FIG. 2 shows a vertical longitudinal section in the center axis of abucket chain excavator according to the invention.

In the drawings are elucidated and respectiely represented a method anda device for making a slit wall. The slit 1 is excavated by means of abucket chain excavator 2 by digging the ground 8 at the front side.

As shown especially in FIGS. la and 1b, the bucket chain excavator 2contains a steel box 3 which is U-shaped with respect to a horizontalsectional plane and which is slightly narrower than the slit 1 to beformed. The bucket chains 4 are arranged so that, running from belowupwards, they break the ground 8 loose and dig it at the front side ofthe slit. There are provided at least two bucket chains 4a and 4b whichare formed so that they are adapted to be telescoped laterally and canrun downwardly within the steel box 3, as the man skilled in the art mayeasily learn from FIGS. la and 1b. The bucket chains 4a and 4b areformed suitably in that the individual buckets are screwed on cables 15.In the present illustrative embodiment, the guidance of the bucketstakes place by means of guide rails 5.

With the aid of sealing sheets 6, the working space surrounded by thesteel box 3 can be separated from the slit region lying therebehind sothat the liquid level 7 in the working space can be lowered incomparison with the liquid level in the slit region lying therebehind.Due to such a lowering, a practically uniformly distributed driveonforce acts on the steel box 3. In this way, it is possible to drive thebucket chain excavator forward and to press the buckets onto the frontside earth 8 as intensely as desired so that an optimum digging capacitycan be achieved.

According to the invention, it is futhermore possible during theconcreting of the slit wall to simultaneously utilize said steel box asa joint shuttering. As shown in FIG. 1a, to this end the back side ofthe steel box 3 is formed in a manner corresponding to the desiredconcreting joint, while at the same time a possibility for incorporatingjoint straps 9 may be envisaged.

In order to prevent fresh concrete from penetrating the free spacebetween the steel box 3 and the lateral earth, the rear corners of thesteel box are provided with further seals 12 which may, e.g., have theform of inflatable hoses of some resilient material.

In order to achieve a reliable detaching of the bucket chain excavator 2from the concrete 13 after the setting thereof, pipes 14 are arrangedwithin the steel box, through which water, a thixotropic liquid or aircan be pressed via nozzles into the joint between the steel box 3 andthe concrete 13. As soon as a sufficiently large gap has been formedafter detaching the steel box from the concrete, the forward drive ofthe bucket chain excavator can be continued in the above-describedmanner according to the invention.

FIG. 1b shows an alternative to the embodiment according to FIG. 1a. Inthis case, the joint shuttering 16 is separated from the bucket chainexcavator 2 during the forward drive and is inserted always prior to theconcreting of the slit wall into the slit so that it abuts the steel box3. In this manner, the diflicult operative phase of the detaching fromthe concrete is avoided at the bucket chain excavator itself, because aliquid column necessary for the forward drive is available at any rateon the back side of the steel box. It is advisable to underprop thejoint shutter ing 16 at the steel box 3 not directly but by means ofdetachable connectors. As shown in FIG. 1b, this can be realized by twoinflatable hoses 18. When the pressure in the hoses is eliminated beforethe resumption of the forward drive, the bucket chains 4 pressed againstthe earth 8 due to the pressure of the fresh concrete will become freeagain and can start running without load.

The drawing of the joint shuttering 16 after resumption of the forwarddrive and after sufficient setting of the concrete 13 can likewise befacilitated by pressing in of I suitable means into the joint betweenthe concrete 13 and the joint shuttering 16. Also, the separatearrangement of the joint shuttering from the bucket chain excavator andrespectively the removal thereof after each use has the advantage thatthe joint straps 9 outside of the slot can be inserted into the jointshuttering in a simple manner.

At the beginning of the forward drive, the liquid level 7 in the workingspace is suitably maintained just as high as in the slit 1 lyingtherebehind, so that the bucket chains 4a and 4b can start runningunloaded. As soon as thixotropic liquid is withdrawn from the workingspace because of the operation of the bucket chains, the liquid level 7drops and the necessary drive-on force becomes effective. In the eventno effective level lowering should be achieved by the operation of thebucket chains 4a and 4b alone, then the liquid 7 can be lowered orrespectively maintained low by additional pumping work. On the otherhand, if the liquid level drops too much during the forward drive, thena thixotropic liquid can flow again in the necessary amount through anopening 11 adapted to be shut off, from the slit 1 into the workingspace.

A guide arm 17 disposed above the level of the terrain serves forcontrolling the drive-on direction of the bucket chain excavator. Ifcurved slit walls have to be made, then the bucket chain excavator 2 canthus be easily rotated about its vertical axis because the steel box 3can be formed sufficiently torsionproof and because the clearancebetween the steel box and the lateral earth permits rotation.

The weight of the bucket chain excavator 2 and the reaction forcesproduced during operation of the bucket chains are suitably received bya gantry crane 10. In this manner, the formation of a vertical slit isensured, and the friction occurring during the forward drive of thebucket chain excavator is minimized. Besides, the depth of the slit canbe varied in accordance with the lifting height of the gantry crane 10.

A particular advantage of the invention is the high digging capacitywhich is achieved in that the bucket chains continuously dig the earth,while at the same time the drive-on force which can be increased at willand which is uniformly effective beyond the depth of the slit is ofdecisive importance.

Thus, it is possible to considerably reduce the time of construction andhence to correspondingly decrease the costs for wages and for materialswhich must be kept in stock. Also, the formation of cavities in thelateral earth is practically out of the question so that a needlesslyhigh consumption of concrete is avoided and completely even slit wallscan be produced.

It is to be understood that the invention is not restricted to thedescribed exemplary embodiments but covers a plurality of modificationpossibilities.

What is claimed is:

1. A method of making slit walls, wherein a slit section present in theground is filled with a fluid and excavated at a front end substantiallycontinuously by means of a bucket chain excavator, wherein the bucketchain excavator is sealed off against the side walls of the excavatedslit and against the sole of the slit so that at the side of the bucketchain excavator facing said front end of the slit and within the slitthere is formed a first fluidfilled space separate from the secondfluid-filled space located behind the bucket chain excavator, whereinthe fluid level in said first fluid-filled space is lowered as comparedto the fluid level in said second fluid-filled space so that the bucketchain excavator is driven forward by the hydrostatic pressuredifferential, and wherein the formed slit is subsequently filled up withconcrete.

2. A method according to claim 1, wherein said slit is filled with athixotropic liquid.

3. A method according to claim 1, wherein the liquid level in said firstliquid-filled space is lowered by the operation of the buckets of thebucket chain excavator.

4. A method according to claim 1, wherein the liquid level in said firstliquid-filled space is lowered by pumping off the liquid.

5. A device for producing slit walls, comprising a bucket chainexcavator which extends down to the sole of the slit wall to be producedand which includes a box which extends along the bucket chains and thebreadth of which is less than the breadth of the slit wall to beproduced, furthermore containing flexible seals for sealing off said boxagainst the side walls of the excavated slit so that spaces separatefrom each other can be formed within the excavated slit in front of andbehind the bucket chain excavator respectively, said spaces beingsubstantially filled with a liquid and means for lowering the liquidlevel in said space located in front of the bucket chain excavator ascompared to the liquid level in said space located behind the bucketchain excavator.

6. A device according to claim 5, including a guide arm secured to saidbox above the level of the terrain for rotation of the bucket chainexcavator so as to permit the production of curved slit walls.

7. A device according to claim 5, wherein said bucket chain excavatorcontains bucket chaims which can be telescoped with respect to thetransverse direction.

8. A device according to claim 5, wherein the back side of said box ofthe bucket chain excavator is formed as a joint shuttering and includesseparate sealing means adapted to be placed on the respective side wallsof the formed slit.

9. A device according to claim 5, wherein at the back side of said boxof the bucket chain excavator there are provided a joint shuttering partextending parallel to said box, as well as separate sealing meansadapted to be laid on the respective side walls of the produced slit.

10. A device according to claim 5, wherein at the back side of said boxof the bucket chain excavator there are provided a joint shuttering partextending parallel to said box, as well as separate sealing meansadapted to be laid on the respective side walls of the produced slit andsecured to said box on both sides thereof, and furthermore whereinbetween said box and said joint shuttering part there are providedpropping means having the form of flexible tubes which are arranged atboth sides near to the walls of the slit that was formed, and which areadapted to be selectively inflated or relieved.

11. A device according to claim 5, wherein the back side of said box ofthe bucket chain excavator is formed as a joint shuttering and includesseparate sealing means adapted to be laid on the respective side wallsof the formed slit as well as pressure conduits which terminate and openin the back side of said box and through which a suitable pressuremedium can be introduced into the joint between said box and theconcrete to thereby detach said box from the solidified concrete of thefinished part of the slit wall.

12. A device according to claim 5, wherein at the back side of said boxof the bucket chain excavator there are provided a joint shuttering partextending parallel to said box as well as separate sealing means adaptedto be laid on the respective side walls of the formed slit, and whereinfurthermore said joint shuttering part includes pressure conduits whichterminate and open in the back side thereof and through which a suitablepressure medium can be introduced into the joint between said jointshuttering part and the concrete to thereby detach said joint shutteringpart from the solidified concrete of the finished part of the slit wall.

13. A device according to claim 5, wherein at the back side of said boxof the bucket chain excavator there are provided a joint shuttering partextending parallel to said box, as well as separate sealing meansadapted to be laid on the respective side walls of the formed slit, andwherein furthermore said joint shuttering part includes a receivingdevice for inserting a joint strap to be concreted therein.

14. A device according to claim 5, wherein said bucket chain excavatoris suspended on a crane.

References Cited UNITED STATES PATENTS 3,385,068 5/1968 Armentrout61-35X 3,416,322 12/1968 Bodine 6135 3,464,665 9/1969 Schoewert 6135XDAVID J. WILLIAMOWSKY, Primary Examiner P. C. KANNAN, Assistant Examiner

